Dilatometric and Thermobarometric Measurements of Truxene Derivatives Exhibiting Inverted and Reentrant Sequences

Abstract

Members of the truxene derivatives series Cn HATX have been investigated by density-temperature—for n = 8 to 12—and thermobarometric—for n = 8, 10 to 13—measurements. Volume changes for transitions, density, partial molar volumes for aromatic cores and CH₂ groups, thermal expansion and isothermal compressibility coefficients are determined for the discoid nematic N_D and rectangular columnar D_rd mesophases. Pressure-temperature phase diagrams for n = 8, 10 to 13 are given; a monotropic phase is observed under atmospheric pressure for n = 10 and 11; it seems it is an hexagonal columnar mesophase D_h. Maximum for the boundary line for D_h and N_D or D_rd phases for n = 10 and 12 are predicted.

Key Words:

• disc-like mesogens
• reentrant sequences
• density
• molar volume
• P-T phase diagram